The present invention relates to improvements in methods of and in apparatus for wet treatment of photosensitive materials, especially color photographic papers. More particularly, the invention relates to improvements in methods of and in apparatus for treating exposed photographic materials. Still more particularly, the invention relates to improvements in methods of and in apparatus for developing, fixing and/or similarly treating exposed photographic films, X-ray films, photographic papers and similar photographic materials, e.g., on their way to a trimming, inspecting, stacking, classifying or other station.
Exposed photographic sheet or web material is normally conveyed through a first vessel wherein it is acted upon by a suitable developing solution, thereupon through a second vessel which contains a suitable fixing bath and, if necessary, through one or more additional vessels containing a rinsing bath, a bleaching bath and/or other liquid media. As a rule, the material is conveyed at a relatively low speed by pairs or other arrays of rollers at least one of which is driven and which serve to advance the material along a predetermined path having successive portions in successive vessels so as to ensure the establishment of predictable contact between the material on the one hand and various liquids on the other hand. When an apparatus is designed for wet treatment of a series of sheets of photosensitive material (such as color photographic paper one side of which has a photosensitive coat or layer), the rollers of the conveying means are preferably submerged in the respective baths so as to educe the cost of cleaning to a minimum. Rollers which extend in part above and in part below the liquid level in a vessel of a developing machine create numerous problems, especially in the region where a sheet leaves the vessel which contains a developing solution to enter a body of fixing solution in the next-following vessel. In many instances, the last rollers in the first tank must advance the sheets vertically or nearly vertically downwardly toward the nip of the first rollers in the second tank. This often entails the accumulation of droplets and/or rivulets or streaks of developing solution on the downwardly advancing sheets. The distribution of such droplets or streaks is not uniform across the width of the sheet which is in the process of entering the fixing bath. This, in turn, results in non-uniform development of the sheets (actually in uncontrollable secondary development of certain portions of the sheets). Moreover, the droplets and streaks prevent predictable bleaching or fixing of the sheets, primarily because the fixing of those portions which carry streaks or droplets of developing solution into the second vessel is delayed as a result of secondary development and also due to the fact that a predetermined interval of time elapses before the droplets and rivulets or streaks of developing solution are admixed to the body of fixing medium in the second bath. In other words, the body of fixing medium in the second bath cannot act upon the photosensitive layer of a sheet in the second vessel with the required degree of predictability and uniformity. The just described conditions are particularly likely to develop when the sheets are transported at a relatively low speed in the range of 5-40 cm/min.
Attempts to solve the just discussed problems involve the utilization of a separate bath (so-called stop bath) which is disposed between the first vessel (developing bath) and the second vessel (fixing bath). The stop bath is capable of collecting at least some droplets and/or rivulets of developing solution ahead of the vessel for the fixing bath; however, the provision of such additional bath contributes to the overall cost and bulk of the developing machine and prolongs the interval of time which is required to complete the development of emulsions on successive sheets or webs.
In accordance with another earlier proposal, the developing machine employs a set of squeezing rollers or squeegees serving to remove the droplets and/or streaks from the sheets which have left the first vessel (containing the developing solution) and are about to enter the second vessel which contains the fixing bath. The squeezing rollers must be uniformly rinsed with fresh water whenever and as long as the developing machine is in use because remnants of developing solution which would be permitted to accumulate on the squeezing rollers would be likely to oxidize and to adversely influence the quality of the next-following sheets. Furthermore, the provision of additional (squeezing) rollers between the first and second vessels and of the means for continuously rinsing the additional rollers with water or the like contributes excessively to the initial and maintenance cost as well as to the bulk of the developing machine.